Underreamer



May 26, 1970 J. v. WATSON 3,513,920

UNDERREAMER Filed June a, 1967 q 73 M 7/ INVENTOR my. 5 John mam TTORNEYS United States Patent 3,513,920 UNDERREAMER John V. Watson, Fort Worth, Tex., assiguor to Watson Manufacturing Company, Fort Worth, Tex. Filed June 8, 1967, Ser. No. 644,685 Int. Cl. E21b 9/26 US. Cl. 175285 9 Claims ABSTRACT OF THE DISCLOSURE Following is disclosed an underreamer having an elongated tubular housing with opposed openings in its cylindrical side wall. Guide slots extend longitudinally along opposed sides of the housing interior to receive the ends of a reciprocal cross bar, which supports a tool joint box for attachment with a kelly depending from a drilling machine. Rotatably secured to opposite ends of the cross bar are two blade holders, each of which has cutting blades secured to its exterior and leading edge. Two operating arms, each having its upper end pivotally secured to a respective blade holder and its lower end pivotally secured to the bottom surface of the housing, are utilized. The cutting edges of the blades on opposite sides of the housing are disposed on the center line of the underreamer, and as seen in plan view, have a cutting surface disposed in a range from to 25 degrees relative to a plane containing the center line and the edge of the cutting surface. Superior cutting action is obtained by disposing such cutting surface at about degrees relative to the above described plane. Additional blades are disposed on the bottom surface of the housing to extend from the edges of associated apertures to clean the bottom of the drilled hole.

Background and general description of the invention In earth boring operations it is frequently necessary to enlarge the bottom region of a drilled hole. Frequently such procedures are utilized when drilling foundation holes for example. The general requirements for an underreamer includes the ability to expand to a large diameter and retract to a small diameter. Necessarily, the mechanism for expanding and retracting the cutter blades must be sufficiently rugged to withstand the destructive reactive forces encountered during earth boring operations. I originated and herein disclose an underreamer having blade holders which are expanded and partially supported by a cross bar reciprocally mounted to guide means located in the interior region of a tubular housing. An oblique operating arm preferably has its upper end pivotally secured to the blade holder beneath the cross bar and its opposite end pivotally secured to a lower region of the housing. Consequently, downward forces exerted on the cross bar in cooperation with the reactive forces from the operating arm urge the blade holder and its associated blade outward. Conversely, upward movement of the cross bar urges the blade holder inward.

The cutting edge of each blade should be positioned as close as practicable to a plane containing the center line of the underreamer, and moreover as previously stated, should have a critically disposed cutting surface. The spoils (or cuttings) which accumulate inside the housing during drilling operations are discharged when raised to the surface of the well bore through utilization of a bafiie plate extending transversely from the operating arms, thereby minimizing time lost in cleaning the underreamer. To insure that the previously established bottom of the bore hole is reached, additional blades are disposed on the bottom of the underreamer adjacent apertures through which cuttings accumulating on the bottom pass into the housing.

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Description of the figures FIG. 1 is a perspective view of an underreamer utilizing the principles of my invention; FIG. 2 is a longitudinal cross section view of the underreamer of FIG. 1; and FIG. 3 is one half of the cross section seen looking along the lines IIIIII of FIG. 2.

Description of a preferred embodiment The numeral 11 in the drawing designates an elongated tubular housing having in this instance two diametrically opposed rectangular openings or doors 13 formed in the side wall (here in the form of a right circular cylinder). Upper and lower plates 17, 19 (see FIG. 2) form the extremities of the housing, with the upper peripheral edge 21 of the housing being inclined inward to form a conical surface to facilitate upward movement of the housing through the drilled hole. The lower plate 19 has at least one but preferably two apertures 23, 25, one of which is disposed adjacent the outer edge of the bottom of a bore hole 27. The other aperture 25 extends from approximately the center line 29 (see FIG. 2) of the housing to an intermediate region of the bottom of the bore hole and plate 19. These apertures have cutting blades 31, 33 which engage the bottom of the bore hole and urge the spoils into the housing.

Longitudinally extending plates 35 are disposed on the interior of the housing, being secured by suitable means such as welding to its interior surface 37 as indicated in FIG. 3. An elongated slot 39 (see especially FIGS. 1 and 2) is formed vertically in each of the plates 39 and receives guide rails 41. The end section 43 of cross bar 45 extends between the guide rails 41 which act as bearing surfaces. Each end portion 43 of the cross bar is turned to a smaller diameter than its central portion to receive a cylindrical sleeve 47 to which is secured a blade holder 49. As shown in FIG. 1, the sleeve 47 and cross bar 45 are disposed on an upper region of the blade holder 49.

Pivotally secured to each blade holder 49 below and outside the cross bar 45 by means of a hinge pin 51 and a hinge support 53 is an operating arm 55. Similarly, the lower end of the operating arm is secured by hinge pin 57 and hinge support 59 to the lower region of the housing and specifically to the lower region of the vertical plate 35 such that the operating arm is obliquely oriented relative to the longitudinal axis 29 of the housing. Extending transversely from the operating arm and substantially along its entire length is a baffle plate 61.

Supported by the cross bar 45 is a connection means 63, here a tool joint box, having an aperture 65 extending transversely therethrough to receive a removable fastener means 67 as shown in FIG. 2. The fastener means is also secured in a mating aperture in the lower region of a kelly bar 69 as indicated in FIG. 2.

A cutting element or blade 71 extends obliquely from the outer edge of each blade holder and as shown in FIG. 3 forms an angle alpha with respect toa plane parallel to the cross bar 45. Also the cutting surface of the blade forms an angle beta with a plane containing the center line 73. To achieve superior cutting of the formation of the bore hole angle beta should be as close as practicable to 20 degrees. Variation of angle beta within a range of 15 to 25 degrees produces less than superior results but is satisfactory under some drilling conditions. Preferably angle alpha is about 25 degrees. The cutting blade should have a toe 75 obliquely formed with respect to the remainder of the blade for cutting the periphery of the hole adjacent the bore hole bottom in a substantially cylindrical fashion as indicated by the numeral 77 in FIG. 2.

In operation a kelly 69 or equivalent is secured to the connection means 63 by means of the fastener 67 and the housing thereafter lowered to the bottom of the bore hole. Slight downward movement of the kelly urges the cross bar 45 downward and the blade holders 49 radially outward due to the cooperative action of the operation arms 55. Such downward movement of the cross bar is effected after kelly 69 and housing 11 are rotated in a clockwise direction as viewed in FIG. 3. The disposition of the cutting blades 71, toe 75, operating arms 55, and cross bar 45 as shown and described causes the blades to be drawn outward into the formation to form a slightly conical surface. By permitting the cross bar to be moved in additional increments downward eventually a bell-shaped bore hole is formed as indicated in FIG. 2. By lifting the kelly 69 with continued rotation of the housing the blade holders 49 are retracted to urge the spoils toward the openings or doors 13 of the housing onto the plate 19. The additinal cutting blades 31, 33 of the plate 19 clean the bottom of the bore hole to enable the selected elevation of the housing to be maintained during successive trips to the bore hole bottom. The housing may be raised to the surface after the blades 71 have been completely retracted. Then the housing is placed on the surface of the ground and the cross bar 45 forced downward. Consequently, the baflles 61 on the operating arms 55 urge as much as seventy-five percent of the spoils from the interior of the housing. After the housing is cleaned of spoils it may be once again lowered to the bore hole bottom to repeat the above described operation until the full extent the bell-shape is obtained. Underreamers of the above type having a housing of 30 inches in diameter have been successfully used to underream a 90 inch diameter bell.

It should be apparent from the foregoing that I have provided an invention having significant advantages. The relationship between the reciprocating cross bar 45, the blade holders 49, the operating arms 55', the blades 71, and the toes 75 is such that the underreamer is essentially self energizing, meaning that the blades urge themselves outward during rotation into the earth formation. It has been found necessary to withhold downward movement of the kelly '69 and cross bar 45 to prevent stalling of the power source. The disposition and configuration of the cutting blades and especially angle beta and the location of the cutting edge on a plane containing the center line of the apparatus has been found especially advantageous. If the cutting edges are located ahead of the center line (with reference to the center line of the underreamer) the blades scrape rather than cut efliciently. Also, if the cutting edges of the blades are located behind the center line, excessive blade bite occurs. Consequently, best results are obtained by placing the cutting edge as close as practicable to the center line of the apparatus. The disposition of the operating arms and the utilization of the bafile plates 61 produces self cleaning of the spoils from the interior of the housing. Under usual operation conditions as much as seventy-five percent of the spoils are urged from the interior of the housing by utilizing this arrangement. The blades on the bottom surface of the housing enable housing elevation to be accurately maintained during successive trips in that the spoils are constantly cleaned from the bore hole bottom during rotation of the housing.

While I have shown my invention in only one of its forms it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes and modifications without departing from the spirit thereof.

I claim:

1. An underreamer comprising:

an elongated tubular housing having opposed openings in the sidewall;

guide means extending longitudinally on opposed sides of the housing interior;

a cross bar extending across the housing into the guide means for reciprocal movement;

two blade holders rotatably secured to said cross bars;

cutting elements secured to the exterior edge of each of said blade holders;

two oblique operating arms, each having one end pivotally secured to a respective blade holder and its other end secured to said housing;

connector means attached to said cross bar for securement to a kelly or equivalent; and

a baffle plate extending transversely from each operating arm to dump spoils from the interior of said housing upon extending said blades.

2. An underreamer comprising:

an elongated tubular housing having opposed openings in the sidewall;

guide means extending longitudinally on opposed sides of the housing interior; I

a cross bar extending across the housing into the guide means for reciprocal movement;

two cutting blade holders rotatably secured to said cross bars; at least one cutting blade secured to the exterior edge of each of said blade holders, said cutting blades having their cutting edges aligned with a plane containing the center line of the tubular housing during extension and retraction of the blade holders;

two oblique operating arms, each having one end pivotally secured to a respective blade holder and its other end secured to said housing; and

connector means attached to said cross bar for securement to a kelly or equivalent.

3. The underreamer of claim 2 in which each of said blades is obliquely secured to a respective blade holder, with the cutting edge forming an angle within a range of 15 to 25 degrees with respect to a plane containing the center line of the housing.

4. The underreamer of claim 2 in which said angle is substantially 20 degrees.

5. The underreamer of claim 2 which further comprises blades disposed on a bottom surface of said housing to extend from edges of associated apertures to clean the bottom of the drilled hole for maintaining a selected underreamer elevation.

6. An underreamer comprising:

an elongated tubular housing having opposed openings in the sidewall;

guide means extending longitudinally on opposed sides of the housing interior;

a cross bar extending across the housing into the guide means for reciprocal movement;

two blade holders rotatably secured to said cross bars;

at least one cutting blade secured to the exterior edge of each of said blade holders; the cutting edge of each blade forming an angle within a range of 15 to 25 degrees with a plane containing the center line of the tubular housing;

two oblique operating arms, each having one end pivotally secured to a respective blade holder and its other end secured to said housing; and

connector means attached to said cross bar for securement to a kelly or equivalent.

7. The underreamer of claim 6 in which said angle is substantially 20 degrees.

8. An underreamer comprising:

an elongated tubular housing having opposed openings in the sidewall;

two oppositely facing, longitudinally extending plate means secured to the interior surface of the tubular housing;

guide means extending longitudinally on opposed sides of the housing interior and secured to respective plate means;

a cross bar extending across the housing into the guide means for reciprocal movement;

two cutting blade holders rotatably secured to said cross bars adjacent the respective plate means;

at least one cutting blade secured to the exterior edge of each of said blade holders; the cutting edges of each blade forming an angle within a range of 15 to 25 degrees with a plane containing the center line of the tubular housing;

two oblique operating arms, each having one end pivotally secured to a respective blade holder and its other end secured to said housing;

connector means attached to said cross bar for securement to a kelly or equivalent;

said plate means functioning to strengthen the tubular housing and support the blade holders during underreaming.

9. The underreamer of claim 8 in which said angle is substantially 20 degrees.

References Cited UNITED STATES PATENTS CHARLES E. OCONN-ELL, Primary Examiner R. E. FAVREAU, Assistant Examiner 

